unbound: Refresh manpages to latest version

Update unbound manpages by copying the current unbound manpages in
contrib/doc/*.in to their respective manpages,

PR: 262013
Reported by: Michael Osipov <michael.osipov@siemens.com>
Fixes: numerous previous updates

(cherry picked from commit 0640e0c1965948da53e0baae9eece957919c0b43)